South Korea's military says North Korea has fired two short-range ballistic missiles into the sea, apparently a response to continuing military exercises by South Korea and the United States.

The South Korean Defense Ministry says the missiles were fired early Thursday morning from North Hwanghae Province. They traveled about 500 kilometers and fell into the water off the country's east coast, officials in Seoul said.

Such firings are not uncommon when animosity rises on the Korean Peninsula. North Korea hates the massive military drills by Seoul and Washington, calling them a preparation for invasion.

Pyongyang also said Thursday it will "liquidate" all remaining South Korean assets on its territory, referring to two abandoned joint projects: the Kaesong industrial complex and the Mount Kumgang tourism resort, both inside North Korean borders.

The North's Committee for the Peaceful Reunification of Korea also said it is nullifying all agreements with South Korea on economic cooperation and exchange programs, and threatened military and economic actions against the South Korean government. The statement was carried by the North's official KCNA news agency.

South Korean assets left at the Kaesong facility are valued at $663 million. It is not clear how the North plans to dispose of them.

Pyongyang also is angry about tough United Nations sanctions imposed following its recent nuclear test and long-range rocket launch.

North Korea has a large stockpile of short-range missiles and is developing long-range and intercontinental missiles.

The North fired six rockets into the sea last week, supervised by leader Kim Jong Un, who ordered his military to be prepared to launch pre-emptive attacks against its enemies.

On Wednesday, Kim said his country has miniaturized nuclear warheads to mount on ballistic missiles.